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Humoral immunity to Streptococcus pneumoniae induced by a pneumococcal ribosomal protein fraction
Abstract:
Isolation of a protective subfraction of ribosomes from Streptococcus pneumoniae has been achieved, and the immune response it induces has been investigated. Mice immunized with pneumococcal ribosomes or purified protein extracted from the ribosomal preparation (2-CE protein) exhibit similar survival rates upon challenge by virulent S. pneumoniae. In contrast, recipients of purified ribosomal ribonucleic acid were never protected against pneumococcal challenge. Serum from mice immunized with pneumococcal ribosomes or 2-CE protein passively immunized syngeneic recipients against pneumococcal challenge, whereas spleen cells from the same donors were unable to transfer immunity. Passive immunization with antiribosome serum could be abrogated by absorption with whole ribosomes, 2-CE protein, or various serotypes of S. pneumoniae (capsular types 2, 3, 6, and 14). Antiribosome serum significantly enhanced clearance of S. pneumoniae from mouse blood in vivo and in vitro. This required phagocytic cells, since antiribosome serum alone, with or without complement, supported growth of S. pneumoniae to an extent comparable to normal serum. The data suggest that the primary immunogen of pneumococcal ribosomes resides in the protein fraction. Further, the immunity induced by the protein fraction is mediated by antibody that appears to function as an opsonin for S. pneumoniae.
Insights
The protein fraction of Streptococcus pneumoniae ribosomes protects mice against infection. Antibodies against this protein act as opsonins, enhancing bacterial clearance by phagocytic cells.
Area of Science:
- Immunology
- Microbiology
- Bacterial Pathogenesis
Background:
- * Streptococcus pneumoniae is a leading cause of bacterial pneumonia and meningitis.
- * Ribosomes are essential cellular components, but their role as immunogens is complex.
- * Understanding protective antigens is crucial for developing effective vaccines against pneumococcal infections.
Purpose of the Study:
- * To isolate and characterize protective subfractions of Streptococcus pneumoniae ribosomes.
- * To investigate the immune response induced by pneumococcal ribosomes and their components.
- * To determine the mechanism of immunity mediated by ribosomal antigens.
Main Methods:
- * Mice were immunized with whole ribosomes, ribosomal protein (2-CE protein), or ribosomal RNA from S. pneumoniae.
- * Immunized mice were challenged with virulent S. pneumoniae to assess survival rates.
- * Passive immunization studies were conducted using serum or spleen cells from immunized mice.
- * Antiribosome serum was tested for its ability to mediate bacterial clearance in vitro and in vivo, with and without phagocytic cells and complement.
Main Results:
- * Immunization with pneumococcal ribosomes or the 2-CE protein fraction conferred significant protection against lethal S. pneumoniae challenge.
- * Ribosomal ribonucleic acid (RNA) failed to protect mice.
- * Serum from immunized mice passively transferred protection, while spleen cells did not.
- * Antiribosome serum enhanced bacterial clearance, dependent on phagocytic cells, and could be absorbed by whole ribosomes, 2-CE protein, and various S. pneumoniae serotypes.
- * The protective immunity was mediated by antibodies acting as opsonins.
Conclusions:
- * The protein component of Streptococcus pneumoniae ribosomes is the primary immunogen responsible for protection.
- * Immunity induced by ribosomal proteins is antibody-dependent and functions via opsonization, enhancing phagocytosis of S. pneumoniae.
- * These findings identify a potential target for novel vaccines against pneumococcal disease.